So I just my first boat, a 1986 Alumacraft Side Console with a 40 hp motor. Boat wasn't running when I first got it so did a basic tune up to get it going. First time on the water it started up fine but would only go about 3mph, if I gave it anymore throttle it would make a grinding noise. It would sound like it was ready to move but not go anywhere. I'm not sure if this is a problem in the lower unit or not but wanted to see if anyone on here had any ideas before taking it somewhere. I know the motor is going up to 30 years old so it could be coming to the end. Any advise is appreciated. Thank you.

Where are you. Could check if needed. I know where a complete good motor is difference is it is a 1989.

I would take you up on checking it out but I'm in Austin.

Sounds like the lower unit may be shot.

That's what I was starting to think also. How would I know this for sure?

Maybe shift linkage adjustment?

Check the lower oil magnet

I have also read where people have similar problems and they just adjusted the shift linkage, but I'm not to sure which linkage is actually being talked about.

Gary, are you saying to check for metal in the oil?

Yes

There was a decent amount of metal shavings but no chips or flakes. I did this the night before going out.

To eliminate the lower unit it will be necessary to remove the lower unit.